1. Field of the Invention
This invention relates in general to rolling shutters for doors, windows and other apertures, and has specific reference to a rolling shutter of the type comprising a first shaft for winding and/or unwinding a sectional structure consisting of blades provided with catch means adapted to be engaged by driving means mounted on and rotatable with a second shaft located downstream of the winding shaft and mounted in lateral flanges of the shutter housing, and guide rails slidably engaged by the side ends of the shutter blades.
2. The Prior Art
It is known to protect the roofs of glass verandahs and attic windows against sun beams by means of a rolling shutter movable in a substantially horizontal plane. In contrast to vertical rolling shutters, horizontal shutters are not responsive to gravity and therefore some means must be provided for moving the sectional structure of a horizontal rolling shutter in either direction.
In a document No. DE-A-2,947,501 there is disclosed a rolling shutter wherein the blades constituting the sectional structure are interconnected by hinge means consisting of a C-section having its two bent ends slidably engaged in slots formed in the longitudinal edges of the blades. These bent ends cooperate with boss means formed in, or rigid with, one wall of said slots. The longitudinal edges of the blades are provided with end members or inserts fitted into the blades. These end members or inserts comprise several studs of which the relative spacing corresponds to the pitch of the driving sprockets.
However, to obtain a proper operation of this rolling shutter the distance between the axes of the first stud of the upstream blade and the first stud of the downstream blade must be the same as the distance between the axes of the various studs rigid with the end members. However, this distance between the axes of the last stud of the upstream blade and the first stud of the downstream blade varies as a function of the direction of travel of the shutter. In a first direction, the shutter movement is obtained by transmitting a thrust from one blade to another. For this purpose, the longitudinal edges of the two adjacent blades contact each other and the distance between the axes of the last stud of the upstream blade and the first stud of the downstream blade has its minimum value.
In the other direction, the sectional structure is driven by a tractive force transmitted from one blade to another through said C-section. Under these conditions, a stretching stress is produced and the distance between the axes of the last stud of the upstream blade and the first stud of the downward blade has its maximum value.
The value of the distance between centers of the studs of said end members corresponds either to the minimum value or to the maximum value, but in no case to both values simultaneously. Thus, in one direction there is compulsorily an alternation between the distance measured between the studs of a same blade and the axial distance between the studs of two adjacent blades. This alternation is inconsistent with the regular pitch of the sprocket teeth.